A pirated, fully functional third-party App Store client for iOS users in China slipped through Apple’s App Store review process and became listed in Apple’s official App Store, researchers at Palo Alto Networks discovered.
Called “开心日常英语 (Happy Daily English),” the application was approved for listing in the App Store where it was listed from Oct 30, 2015 through Feb 19, 2016, when Apple became aware of its functionality and removed it. Palo Alto’s Claud Xiao explains that the program did not display malicious functionality, but was classified as “riskware”.
The security researchers who discovered the pirated App Store client call it “ZergHelper” and say that enterprise-signed versions of the program were also found elsewhere in the wild. They say that the application managed to trick Apple’s app review process by displaying different behaviors for users, based on their geography.
For example, the tool works as an English studying application for users living outside China, while its actual features appear only when accessed from devices in China. ZergHelper went unnoticed for almost 4 months, but drew attention on Feb 19, when a user created a post on a Chinese developer forum to discuss it. Apple was informed of the issue the same day and removed the app on Feb 20.
The main functionality of ZergHelper is that it provides users with another App Store that allows them to download and install pirated and cracked iOS apps and games. Developed by a Chinese company, the program is the non-jailbroken and “official App Store” version of a product called “XY助手 (XY Helper).”
Once installed on an iOS device, the app is displayed under the name of XY Helper, and it automatically tries to connect to interface[.]xyzs.com. The connection fails for IPs outside China, where the app displays an English study interface and has no additional functionality available for users, but succeeds in the China, prompting users to install two configuration profiles.
All of the applications and games available for download via ZergHelper are free including pirated versions of popular legitimate apps. Users can provide their Apple ID and password, but also have the possibility of receiving an Apple ID for free, but the researchers weren’t able to determine where these Apple IDs came from.
Although not a malicious app by itself, ZergHelper poses several risks to users, mainly by allowing them to install modified versions of iOS apps whose security can’t be ensured. Moreover, the pirated storefront abuses enterprises certificate and personal certificates for the signing and distribution of apps, which may include code that hasn’t been reviewed.
At the same time, the program asks users to enter their Apple ID, shares some Apple IDs to users, and logs in to an Apple server using these IDs to perform many operations in background. Through dynamic code updates, the app’s author could extend its capabilities, which could further bypass iOS security restrictions, the researchers say.
To install apps on non-jailbroken devices, the risky app re-implements a small version of Apple’s iTunes client for Windows to login, purchase and download apps. By implementing some functionalities from Apple’s Xcode IDE, it can also generate free personal development certificates from Apple’s server to sign apps, thus abusing the developer program Apple introduced about eight months ago.
The novel techniques this third-party store uses are sensitive and risky and could be used by malware to attack the iOS ecosystem, especially since the tool can sign apps and devices. By using the programming language Lua, the app’s authors tried to make it more extensible, not to mention that the framework allows authors to update code without going through Apple’s review process.
Overall, researchers have identified over 50 ZergHelper apps signed by enterprise certificates, which spread through various channels. One thing that is uncertain at the moment is whether the app is capable of stealing account information and sending it back to the server, although the software did sent back some device information for statistic tracking.
Apple’s Xcode development tool has been targeted by cybercriminals before, and a rogue version of the IDE called XcodeGhost was spotted in September. It was capable of injecting malicious code into iOS and OS X applications. In November, the malicious tool was updated to target iOS 9, the latest major platform release for Apple’s mobile devices.
Full details on ZergHelper are available from Palo Alto Networks.